This invention relates to an apparatus and a method for installing valves directly on or into an existing pipe. The pipe may be a new or an old installation; it may be empty or fluid filled under full pressure, and the pipe may consist of any suitable material.
Those persons knowledgeable with valve repair and replacement know the frustration of dealing with seized and leaking valves which cause equipment shutdowns and are very time consuming to replace. There is a need to provide a new type of valve which may be installed on existing pipes quickly, completely, and which does not require specialized equipment or training.
Today's valves were basically designed for installation into new piping systems by flanging, threading or welding. These attachment methods are extremely difficult and time consuming because the entire piping system must be shut down and drained before installation can begin. Shutting down the system or having the system break down in an emergency can easily cost thousands of times the price of the failed valve in lost production, poor quality product or environmental spills. Emergency repairs or mill shut downs are caused many times due to seized or leaking valves.
Vast numbers of valves are installed on existing pipes each year throughout the world. They provide shut off, by-pass, automatic control, allow installation of new equipment and/or prevent environmental spills. Each installation is very labour intensive and time consuming as the existing pipe must be cut through with saws or torches, attachments added such as welded-on flanges or threaded pipe ends, and the new valve bolted, threaded or welded into place.
Technology presently exists to install branch connections into main lines which are in service. Basically, small branch lines are used to attach instruments or by-passes to a main pipe while leaving the main pipe intact and undisturbed. These "hot-tap" connections were never designed to shut off or control flow in the main pipe.
Other technology exists to shut off flow in a main line while in service. Basically these are large, complicated, expensive, labour intensive, specialty devices used for a one-time shut off during an emergency situation. The following is a summary of typical prior art of this type including some of their associated problems.
1. Rubber Bladder--rubber bladders are placed into the main line through a small branch connection and inflated with compressed air to seal against the inside wall of the pipe. These rubber bladders are easily cut, can stop but not control flow, and were designed for one time emergency operation.
2. Tapered Metal Plug--the top half of an existing pipe is cut off and a full sized tapered steel plug is set into the line. The existing-pipe wall must be cut and then machined to give a good mating surface for the plug to seal against. This method requires highly specialized operators, a large apparatus to seal during consecutive steps in the operation, is expensive, yields much contamination due to the cutting operation and requires the new housing to be welded to the existing pipe. These plugs were designed to install full size branch connections or to shut off main line flow at high temperatures during extreme emergency situations.
3. Downstream Disc--the top half of the existing pipe is cut off in successive actions as described above. A full size disc is passed through the branch connection to seal against the inside of the existing pipe. This method has all the disadvantages listed in item No. 2 and was designed for one-time emergency shut-off of main line flow. 4. Hydraulic Shear/Score Tool/Saw--these methods include cutting completely through the existing pipe and welding the valve housing to the pipe for structural integrity. These are the largest, most complicated systems. These procedures may be very time consuming and should be performed by a machinist-type operator. 5. Oil Wells--a number of methods have been designed specifically for the oil industry to cap well heads. Basically these systems were designed to shut off flow in a center pipe after cutting through two concentric outer pipes. Many of the highly specialized devices are so specific that they do not apply to the situations commonly encountered in industrial plants.